1. Field of the Invention
The invention relates to oil well drilling and production. More particularly, the invention relates to a system for remote actuation of downhole tools employing chemical triggers.
2. Prior Art
For as long as wells have been drilled for any purpose whatsoever, actuating various tools that have been placed downhole has been of concern. The tool can be at tremendous depths and in conditions where communication is quite difficult. Some methods for communication to downhole tools are pressure pulses, short hop communications, acoustic telemetry wireline and permanent electrical conductors. All of these are certainly capable of providing necessary communication to the downhole tools and have been used for years. Because of inherent drawbacks in these methods however, the search for a more reliable and predictable actuation method and system continues. One of the inherent drawbacks is voids in the fluid column. Voids in the fluid column significantly hamper efforts to propagate wave form communication of any kind through the fluid in the wellbore because the xe2x80x9cwavexe2x80x9d tends to collapse when it hits the interface between liquid and gas. To some extent, of course, the wave will continue but it certainly will be diminished. Thus when the tool to be communicated with is a long distance from the surface or other decision making location, communication there to may require several tries before being successful. One of the more efficient wave form communication techniques is pressure pulsing the well since although the voids in the fluid column are compressible, the pulse at least to some extent will travel through the void and continue in the liquid on the other side thereof. While wave propagation communication techniques are often used in the well industry, a more efficient form is desired.
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the downhole tool actuation system of the invention.
The invention provides an actuation system for activating a downhole tool, whether that tool be a controller or other type of tool, (e.g. an environment modifying tool) by providing a chemical sensor in the downhole environment at a predetermined location and adapted to detect a certain chemical component. The chemical sensor may be directed to chemicals that are not naturally occurring in or normally introduced to the wellbore or can be adapted to sense chemicals which are indigenous to the system depending upon what use is to be made of the sensor. In the non-naturally or normally occurring embodiment of the invention, the sensor detects chemicals that are introduced to the well for the sole purpose of activating a tool upon sensing the chemical, the sensor generates its own millivolt impulse which is transmitted to a desired location to actuate a tool, provide intelligence downhole or be counted by a counter on its way to a full count and the execution of instructions. This provides for an accurate and non-environmentally effected actuation of downhole tools. The method also avoids stressing components of the system as is the case for prior methods like temporarily pressurizing the tubing, etc.
In the environmental embodiment of the invention, the chemical sensor will be adapted to sense chemical components that are inherent in the well. This may be from breakthrough fluids or may result from other operations, or may even be a part of the desired fluids. Since knowledge in the art allows for predictions of these chemicals, sensors can be used to change the well environment by causing the opening or closing of sleeves, etc. or provide pin point times for when expected occurrences actually do occur. The chemical sensors of the invention may be employed singly, in groups of the same chemical sensors, in groups of different chemical sensors or in groups with sensors for other types of parameters such as pressure, temperature, flow rate etc. In embodiments where groups of different types of sensors are employed for a single actuation, premature actuation is less likely due to the need for more than one occurrence to happen.
The chemical sensor may be operably connected to a controller of any level of xe2x80x9cintelligencexe2x80x9d.
Two other preferred embodiments of the invention employ a similar concept in that a chemical is employed to actuate a downhole tool however the chemical is an active part of the actuator for the tool as opposed to something that is only sensed by a sensor which then provides a signal. Rather, in these embodiments, the chemical is actually used to create an electrical connection that provides for actuation. In one of the embodiments, the chemical is employed to dissolve an encapsulation material so as to create an electrical connection downhole. In the other embodiment, the chemical is an electrolyte which completes a battery downhole and begins the actuation process in that manner. It should be understood however that these embodiments are exemplary in nature and that any type of sensual chemical or chemical property can be employed without departing from the spirit and scope of the invention. Chemicals include radioactive and non-radioactive isotopes and properties include conductivity, resistivity, ion-activity, pH, etc.
In a further aspect of the invention, chemicals are used as a communication tool wherein the tool will confirm that it is properly set by releasing a particular chemical after a setting process. Moreover, the invention contemplates communications, particularly in connection with inflatable tools where the inflatable tool itself is filled with a chemically tagged fluid such that in the event the inflatable tool ruptures or otherwise releases the fluid intended to be maintained therein, such fluid will be easily identifiable at the surface which will signify that a downhole tool has failed. The invention further can identify which downhole tool has failed by using different chemical taggants for each of the inflatable tools employed in a well. Thus, when a particular taggant is identified at the surface, a particular inflatable tool is known to have failed.
Another chemically based actuation tool of the invention is a water-cut sensor which automatically actuates the tool to which it is associated. When the water-cut of the produced fluid reaches a predetermined or selected value the sensor signals the actuator to close and further flow from the area will be halted. One practical application for such chemical actuation is a sliding sleeve which can be shut off when water begins to infiltrate the well. By providing a chemical sensor capable of sensing water at a certain percentage, the tool is much more quickly closed than it would have been had sensing for water been carried out at the surface.
Yet another aspect of the invention provides communication to the surface from a downhole tool which because of an event in its vicinity, has released a chemical into the well production fluid. This embodiment of the invention would preferably use a particular taggant chemical so that when such chemical is identified at the surface it will point directly to the tool at which such event has occurred.
In the final aspect of the invention, chemical communication using tracer gas is also contemplated. One embodiment employing such a tracer gas is wherein a gas lift mandrel is being employed. A tracer chemical is introduced to the lift gas at the surface, or other lift gas introduction location, which tracer chemical is sensual by the gas lift mandrel and will trigger adjustments of the gas lift valves in the gas lift mandrel.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.